Commit f3414bc7 authored by David Matlack's avatar David Matlack Committed by Radim Krčmář
Browse files

kvm: x86: export maximum number of mmu_page_hash collisions 



Report the maximum number of mmu_page_hash collisions as a per-VM stat.
This will make it easy to identify problems with the mmu_page_hash in
the future.

Signed-off-by: default avatarDavid Matlack <dmatlack@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 826da321

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -821,6 +821,7 @@ struct kvm_vm_stat { 
	ulong mmu_unsync;

	ulong remote_tlb_flush;

	ulong lpages;

	ulong max_mmu_page_hash_collisions;

};



struct kvm_vcpu_stat {

arch/x86/kvm/mmu.c

+17 −8
Original line number Diff line number Diff line
@@ -1904,17 +1904,17 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm, 
 * since it has been deleted from active_mmu_pages but still can be found

 * at hast list.

 *

 * for_each_gfn_valid_sp() has skipped that kind of pages.

 * for_each_valid_sp() has skipped that kind of pages.

 */

#define for_each_gfn_valid_sp(_kvm, _sp, _gfn)				\

#define for_each_valid_sp(_kvm, _sp, _gfn)				\

	hlist_for_each_entry(_sp,					\

	  &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)], hash_link) \

		if ((_sp)->gfn != (_gfn) || is_obsolete_sp((_kvm), (_sp)) \

			|| (_sp)->role.invalid) {} else

		if (is_obsolete_sp((_kvm), (_sp)) || (_sp)->role.invalid) {    \

		} else



#define for_each_gfn_indirect_valid_sp(_kvm, _sp, _gfn)			\

	for_each_gfn_valid_sp(_kvm, _sp, _gfn)				\

		if ((_sp)->role.direct) {} else

	for_each_valid_sp(_kvm, _sp, _gfn)				\

		if ((_sp)->gfn != (_gfn) || (_sp)->role.direct) {} else



/* @sp->gfn should be write-protected at the call site */

static bool __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
@@ -2116,6 +2116,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, 
	struct kvm_mmu_page *sp;

	bool need_sync = false;

	bool flush = false;

	int collisions = 0;

	LIST_HEAD(invalid_list);



	role = vcpu->arch.mmu.base_role;
@@ -2130,7 +2131,12 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, 
		quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1;

		role.quadrant = quadrant;

	}

	for_each_gfn_valid_sp(vcpu->kvm, sp, gfn) {

	for_each_valid_sp(vcpu->kvm, sp, gfn) {

		if (sp->gfn != gfn) {

			collisions++;

			continue;

		}



		if (!need_sync && sp->unsync)

			need_sync = true;
@@ -2153,7 +2159,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, 


		__clear_sp_write_flooding_count(sp);

		trace_kvm_mmu_get_page(sp, false);

		return sp;

		goto out;

	}



	++vcpu->kvm->stat.mmu_cache_miss;
@@ -2183,6 +2189,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, 
	trace_kvm_mmu_get_page(sp, true);



	kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);

out:

	if (collisions > vcpu->kvm->stat.max_mmu_page_hash_collisions)

		vcpu->kvm->stat.max_mmu_page_hash_collisions = collisions;

	return sp;

}

arch/x86/kvm/x86.c

+2 −0
Original line number Diff line number Diff line
@@ -190,6 +190,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { 
	{ "mmu_unsync", VM_STAT(mmu_unsync) },

	{ "remote_tlb_flush", VM_STAT(remote_tlb_flush) },

	{ "largepages", VM_STAT(lpages) },

	{ "max_mmu_page_hash_collisions",

		VM_STAT(max_mmu_page_hash_collisions) },

	{ NULL }

};

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